This invention relates to an ulra-high speed data and communication link, and in particular to a hybrid WDM-TDM transmitter capable of simultaneously generating up to twenty or more tunable WDM channels using a single-striped Ga As/AlGaAs type semiconductor optical amplifier, and was funded in part by the National Science Foundation ECS contract number 9522267, and is a Continuation-in Part of U.S. patent application Ser. No. 09/096,271 filed Jun. 11, 1998, now U.S. Pat. No. 6,256,328. This application claims the benefit of provisional applicaition No. 60/0855,566.
Ultra high speed data links will become wide spread with the deployment of broadband switched digital networks and services, e.g., teleconferencing, video telephony, and computer services. The key hurdle in the commercial development of these networks is the availability of cost effective photonic technologies that will speed up the generation, transmission and processing of these vast amounts of data. Present state of the art optical communications and signal processing rely on a wavelength division multiplexed (WDM) or a time division multiplexed (TDM) hardware platform.
Thus, hardware based on multiwavelength optical signal sources capable of generating ultrashort and highly synchronized picosecond pulses are of great interest in novel photonic networks utilizing combined optical wavelength division multiplexed (WDM) and time division multiplexed (TDM) data formats. To date, multiwavelength generation has been demonstrated by either using spectral filtering of femtosecond optical pulses, or semiconductor laser based devices. See Morioka et al., xe2x80x9cMulti WDM-Channel pulse generation from a Single Laser Source utilizing LD-pumped Supercontinuum in Optical Fibersxe2x80x9d, PhotonTech. Lett., vol.6, no.3, 365xcx9c368, 1994: and Nuss et al. xe2x80x9cDense WDM with Femtosecond Laser Pulsexe2x80x9d, IEEE/LOS 1994 Annual Meeting, Boston, Mass., 1994
In these approaches, the main idea is to generate femtosecond optical pulses at a low channel pulse rate. These approaches generally suffer from limited wavelength channels, the need of high power laser source, system complexity, and low single channel rates.
Furthermore, there have been various patents of general interest in this area that also fail to overcome the problems described above. U.S. Pat. No. 4,435,809 to Tsang et al. describes a passively mode locked laser having a saturable absorber that only has a single wavelength operation mode, with multiple longitudinal modes. U.S. Pat. No. 4,446,557 to Figueroa describes a mode-locked semiconductor laser with tunable external cavity where a user adjusts the cavity length which modifies the longitudinal mode spacing to generate a single wavelength output. U.S. Pat. No. 5,115,444 to Kirkby et al. describes a multichannel cavity laser where each wavelength is generated from a common cavity with each wavelength experiencing a different optical path length. Simultaneous generation of each wavelength is not feasible since the gain competition in the final optical amplifier stage will complicate and prevent simultaneous multiwavelength generation. U.S. Pat. No. 5,228,050 to LaCourse et al. describes an integrated multiple-wavelength laser array, each wavelength having its own cavity that is length adjustable to allow lasing at different wavelengths, and requires an array of lasers for the multiple wavelength generation. U.S. Pat. No. 5,319,655 to Thornton describes a multiwavelength laterally-injecting type lasers which requires the sources to be precisely aligned to one another. U.S. Pat. No. 5,524,012 to Wang et al. describes a tunable, multiple frequency laser diode that uses a multistripe semiconductor laser array to generate several wavelengths, and requires a grazing incidence angle on the diffraction grating. Using the grazing incidence angle prevents simultaneous wavelength generation. U.S. Pat. No. 5,524,118 to Kim et al. describes a wavelength-varying multi-wavelength optical filter laser using a single pump light source, which requires using an erbium doped fiber amplifier. U.S. Pat. No. 5,561,676 to Goldberg describes a compound-cavity high power, tunable modelocked semiconductor laser, that generates a single wavelength output that does not allow for multiple wavelength generation.
Another problem with multichannel generation from femtosecond lasers is that the multiple channels are generated by spectrally filtering the laser output after the optical pulse is generated. This is inefficient because the filtering process eliminates, or throws away, energy that was used in making the optical pulse.
In approaches relying on the spectral filtering of super-continuum generation, some wavelength channels may experience excess spectral incoherence, rendering them useless for data transmission.
The first objective of the present invention is to provide an ultra-high speed data and communication link based on an actively modelocked laser with multiple wavelength generation.
The second object of this invention is to provide an ultra-high speed photonic circuit based on multiwavelength generation from a semiconductor diode laser source.
The third object of this invention is to provide an ultra high-speed data and communication link based on generating multiwavelengths simultaneously from a single stripe semiconductor diode laser source.
The fourth objective is to provide a method for switching and routing, multiple wavelengths simultaneously.
The subject invention hybrid WDM-TDM optical link includes a hybrid modelocked multiwavelength semiconductor laser that can simultaneously generate over 20 independent wavelength channels at rates greater than approximately 5 Gbits per second. Additionally, ultrafast optical demultiplexing that relies on an all optical clock recovery technique and nonlinear optical loop mirrors is used to demultiplex multiwavelength data down to rates suitable for electronic photoreceivers. The temporal duration of the optical pulses would mean that aggressive temporal interleaving can lead to optical data and transmission systems operating at rates in excess of approximately 800 Gbits per second, based solely on the semiconductor optical amplifier applications.
Further objects and advantages of this invention will be apparent from the following detailed description of a presently preferred embodiment which is illustrated schematically in the accompanying drawings.